1. Field of the Invention
This present invention relates to a method for forming a film, and more specifically to a method for forming a film on a substrate, the method can control a thickness of the film formed on the substrate.
2. The Related Art
Sol-Gel method is used to form SiO2 film, TiO2 film, ZrO2 film, etc. The film formed by the Sol-Gel method has a good chemical uniformity, an easy forming process and a lower cost, and suits to coat various substrate, so the film formed by the Sol-Gel method is used widely. Metal alkane oxide (precursor), dissolvent, deionized water and catalyst are blended to form sol solution, then the sol solution undergoes hydrolyzing, condensing and polymerizing to form gel solution slowly, the gel solution is coated on a substrate to form a film.
Nevertheless, the ratio of the metal alkane oxide, the dissolvent, the deionized water and the catalyst, the forming condition and the environment factor can effect the thickness of the film formed by the Sol-Gel method. Of course, when the film is made by the sol-gel method, the thickness of the film can be controlled by adjusting the ratio of the metal alkane oxide, the dissolvent, the deionized water and the catalyst. But, if the ratio of one of the metal alkane oxide, the dissolvent, the deionized water and the catalyst is adjusted, the entire ratio relation of the film will be changed, then the thickness of the film is not easy to be controlled. If the ratios of the metal alkane oxide, the dissolvent, the deionized water and the catalyst are adjusted at the same time, the thickness of the film can be controlled, but this operation is very complex.